Do you know the wind loading vs pull-out resistance of the threads? This is why I am happy to have the services of a structural engineer, as required by our County for all roof-mounts for the last 4 years or so. At first it was an annoyance to have the extra time and expense of a PE analysis for each job, but now that it's incorporated into our practices, I certainly sleep better during windstorms. We often have to provide more attachments than our seat-of-the-pants approach would have resulted in, but we no longer have liability for it.
I imagine your threaded proposal is based on the lack of access to the underside of the roof for a through-bolted solution. There has been some discussion in the past of toggle type fasteners for this situation. Bruce Erickson Mendocino Solar Service PO Box 1252 Mendocino, CA 95460 707-937-1701 On Apr 21, 2011, at 2:27 PM, North Texas Renewable Energy Inc wrote: > Wrenches > > I'm proposing a PV array on a metal building with L feet attached directly > thru the roof into the purlins. The plan is to use thread cutting SS bolts, a > minimum of ¼-28 pitch. The metal is 14 ga and will engage over 2 full threads > and because the array is only 2 landscape modules on NS rails there will be 2 > bolts for every module. 36 total. Im using a mag base drill press so the144 > holes will be straight & round. > What surprises can I expect or is there an easier way to go about this. Your > 2¢ is welcome. > > Jim Duncan > North Texas Renewable Energy > 486 W.N. Woody Road > Azle Texas 76020 > NABCEP Certified Solar PV > Installer No.031310-57 > TECL 27398 > nt...@1scom.net > 817.917.0527 > www.ntrei.com > > > <North Texas Renewable Energy > Inc.vcf>_______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org >
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